There is a process called the Lost Foam method. We use it to make High speed RC gliders. Do some research on google and Im sure you will find some good how to's. It basically takes a piece of foam that you shape then glass over it with resin and carbonfiber for strength. then once the resin is set you use acetone to melt the foam away. and you are left with a clean fiberglass hull to work with. Keep me posted on your progress. I would really like to see what you come up with. I have access to some wacker motors I could play with. Might be interesting.
Shawn